/// isPowerOfTwo - Return true if the given value is known to have exactly one
/// bit set when defined. For vectors return true if every element is known to
/// be a power of two when defined. Supports values with integer or pointer
- /// type and vectors of integers.
- bool isPowerOfTwo(Value *V, const TargetData *TD = 0, unsigned Depth = 0);
+ /// type and vectors of integers. If 'OrZero' is set then returns true if the
+ /// given value is either a power of two or zero.
+ bool isPowerOfTwo(Value *V, const TargetData *TD = 0, bool OrZero = false,
+ unsigned Depth = 0);
/// isKnownNonZero - Return true if the given value is known to be non-zero
/// when defined. For vectors return true if every element is known to be
/// bit set when defined. For vectors return true if every element is known to
/// be a power of two when defined. Supports values with integer or pointer
/// types and vectors of integers.
-bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, unsigned Depth) {
- if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
- return CI->getValue().isPowerOf2();
- // TODO: Handle vector constants.
+bool llvm::isPowerOfTwo(Value *V, const TargetData *TD, bool OrZero,
+ unsigned Depth) {
+ if (Constant *C = dyn_cast<Constant>(V)) {
+ if (C->isNullValue())
+ return OrZero;
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
+ return CI->getValue().isPowerOf2();
+ // TODO: Handle vector constants.
+ }
// 1 << X is clearly a power of two if the one is not shifted off the end. If
// it is shifted off the end then the result is undefined.
return false;
if (ZExtInst *ZI = dyn_cast<ZExtInst>(V))
- return isPowerOfTwo(ZI->getOperand(0), TD, Depth);
+ return isPowerOfTwo(ZI->getOperand(0), TD, OrZero, Depth);
if (SelectInst *SI = dyn_cast<SelectInst>(V))
- return isPowerOfTwo(SI->getTrueValue(), TD, Depth) &&
- isPowerOfTwo(SI->getFalseValue(), TD, Depth);
+ return isPowerOfTwo(SI->getTrueValue(), TD, OrZero, Depth) &&
+ isPowerOfTwo(SI->getFalseValue(), TD, OrZero, Depth);
+
+ Value *X = 0, *Y = 0;
+ if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
+ // A power of two and'd with anything is a power of two or zero.
+ if (isPowerOfTwo(X, TD, /*OrZero*/true, Depth) ||
+ isPowerOfTwo(Y, TD, /*OrZero*/true, Depth))
+ return true;
+ // X & (-X) is always a power of two or zero.
+ if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X))))
+ return true;
+ return false;
+ }
// An exact divide or right shift can only shift off zero bits, so the result
// is a power of two only if the first operand is a power of two and not
match(V, m_UDiv(m_Value(), m_Value()))) {
PossiblyExactOperator *PEO = cast<PossiblyExactOperator>(V);
if (PEO->isExact())
- return isPowerOfTwo(PEO->getOperand(0), TD, Depth);
+ return isPowerOfTwo(PEO->getOperand(0), TD, OrZero, Depth);
}
return false;
}
// The sum of a non-negative number and a power of two is not zero.
- if (XKnownNonNegative && isPowerOfTwo(Y, TD, Depth))
+ if (XKnownNonNegative && isPowerOfTwo(Y, TD, /*OrZero*/false, Depth))
return true;
- if (YKnownNonNegative && isPowerOfTwo(X, TD, Depth))
+ if (YKnownNonNegative && isPowerOfTwo(X, TD, /*OrZero*/false, Depth))
return true;
}
// X * Y.